Function ndArrayLen

Computes the minimum valid Float32Array length for a param from its dependsOn and dims.

• dependsOn contains an "ld*" field → matrix, sized via matrixShape: (outer-1)*ld+inner
• dependsOn contains "trans" (and m is in dims) → L2 vector: size from dims.trans
• otherwise → L1 vector: (n-1)*inc+1

Shared by resolveNdArray (validation) and buildArb (fixtures) to keep formulas in sync.